Well probes may be associated, for example, with a train of drill and thrust rods as far as inside the extremely steep contorted well sections as part of acoustic or seismic exploration operations.
For example, a well equipped for the production of hydrocarbons comprises a casing string installed during drilling operations. The casing string is held in place with cement injected into the annular space between this casing and the drilling. In the cased well, a tubular column or tubing is installed to allow fluids to flow outside the production zone.
The well probe of the invention makes it possible to install acoustic or seismic sensors in a production well so as to take seismic readings. These type of readings in a reservoir are useful for determining its gradual evolution. For example, a method, known as a vertical seismic profile method (VSP), is used, with this method comprising the receiving of waves sent back by underground reflectors by one or more sensors disposed in one or more well probes lowered along a drilling, with the waves having being emitted by a seismic generator disposed on a surface or even in another well.
The taking of seismic readings in a fitted well requires the installation of a set of sensors and this may only be effected by stopping the production operations. French Patent 2,593,292 (or corresponding U.S. Pat. No. 4,775,009) describes a method and a device for installing a seismic reception unit in a well. The method mainly consists of providing sensors outside the casing and embedding the sensors in cement injected into the annular space. French Patent 2,642,849 (or corresponding U.S. patent application Ser. No. 477,503 now U.S. Pat. No. 4,986,350) also describes a device for anchoring an acoustic or seismic reception unit outside a casing prior to it being cemented in a drilling. The device provides for protection of this control unit against any impacts when installing the casing. Advantageously, such a method and devices make it possible to soundly couple the sensors with the land surrounding the well. On the other hand, coupling of a seismic device by bore hole cementation is irreversible which may sometimes prove to constitute a drawback. More particularly, after bore hole cementation, the installation is definitive in that the reception unit cannot be recovered if the controlled well is less productive than initially anticipated and a defective sensor cannot be changed. Moreover, after the start of an operation, it is sometimes found that certain wells are more particularly promising and that it would be advantageous to install a set of sensors in these already tubed wells.